Surface Heat Pumping Loss in a Pulse Tube Refrigerator

Abstract

Surface heat pumping in pulsetube refrigerator is caused by oscillating heat transfer between the tube wall and the inside gas of the pulse tube. It is equivalent to shuttle heat transfer in GM or Stirling cryocooler and, therefore, acts as loss. In this paper, the surface heat pumping effect is analyzed for idealized orifice pulse tube refrigerator. The linearized fluid equations without thermal diffusion effect and with thermal diffusion effect in the pulse tube were solved analytically. From the solutions the time-averaged enthalpy flows were calculated for both cases. Since the thermal diffusion effect causes the difference in the enthalpy flows, the difference is equal to the net effect of the thermal diffusion effect, or equivalently, surface heat pumping effect. The surface heat pumping effect is heavily dependent on the pulse tube geometry and the operating parameters. It is not negligible in small-size or low frequency pulse tube refrigerators according to the analysis. To reduce this loss, the pulse tube is suggested to have small thermal mass so that the wall temperature can follow the bulk temperature.